1. Field of the Invention
The present invention relates to a color selecting mechanism used for a color cathode ray tube.
2. Background of the Invention
As a color selecting mechanism for a color cathode ray tube, for example, as shown in FIG. 1 and FIG. 2 (enlarged view of an essential portion), a color selecting mechanism 31 called an aperture grill is known. The color selecting mechanism 31 is provided with a frame-like metal frame 36 formed of a pair of supporting members 32 and 33 opposing each other and elasticity applying members 34 and 35 which are stretched between both end portions of the supporting members 32 and 33, and a mask member, that is, a color selecting electrode thin plate 40 in which a number of vertical slit shaped electron beam penetrating apertures 39 are arranged in one direction, that is, along a horizontal direction of a picture screen stretched between the opposing supporting members 32 and 33 on the frame 36.
The color selecting electrode thin plate 40 is made of a thin metal plate which is structured by arranging a number of thin band shaped grid elements 38 in the above mentioned one direction at a predetermined pitch, and by forming a long slit shaped electron beam penetrating 39 in a vertical direction of the picture screen between the respective neighboring grid elements 38 and in which the grid elements 38 are stretched between the supporting members 32 and 33 with a predetermined tension by the elasticity applying members 34 and 35. The color selecting electrode thin plate 40 is fixed onto the opposing supporting members 32 and 33 of the frame 36 by means of seam-welding. In FIG. 2, reference numeral 47 shows an orbit of the seam-welding.
In the color selecting mechanism 31, in order to prevent the grid elements 38 from vibrating, a damper wire 42 is stretched along an arranging direction of the grid elements 38 in contact with a surface of the color selecting electrode thin plate 40. The damper wire 42 is stretched through damper springs 44 fixed respectively onto the opposing elasticity applying members 34 and 35 of the frame 36.
Reference numeral 45 shows a supporting spring for fixing the color selecting mechanism 31 to a panel of a color cathode ray tube. The supporting spring 45 is welded on four sides of, for example, the supporting members 32 and 33, and the elasticity applying members 34 and 35 through a spring holder 43.
By the way, in the above color selecting mechanism 31, when it is applied with a vibration, the attenuation of the grid element 38 at a portion corresponding to a center of the picture screen is very slow. Therefore, in the color cathode ray tube equipped with the above mentioned color selecting mechanism 31, at a time of being applied with the vibration, there has occurred a change in brightness called a uniformity deterioration, thereby causing a problem.
Meanwhile, in the color selecting mechanism 31, as mentioned above, a plurality of the damper wires 42 are stretched along the surface of the color selecting electrode thin plate 40 in order to prevent the above-mentioned vibration, so shadows of the damper wires 42, that is, so-called damper shadows occur in the picture screen. Particularly, in a cathode ray tube of a fine pitch, that is, high definition, the damper shadows are conspicuous.